1. Field of the Invention
The present invention relates to a procedure for the manufacture of bound textile sheets by introduction of an acrylic resin dispersion free of formaldehyde and of substances yielding formaldehyde. In addition, the invention relates to textile sheets manufactured by this process.
2.Description of the Background
Bound textile sheets have been manufactured in the past which exhibit outstanding wet tensile strength and fastness in water and to washing with lye. During manufacture, textile sheets are treated with aqueous acrylic resin dispersions, the synthetic resin component of which contain cross-linking amido-methylol groups. When the treated textile sheets area is dried, small quantities of formaldehyde are normally liberated, which formaldehyde raises health-related problems. Because of the objectionable release of formaldehyde, binders for textile sheets have been sought which have wet tensile strength and fastness to water and washing lye sufficient for practical purposes, but which do not yield formaldehyde when heated.
German Pat. No. 3,202,122 discloses a method of fixing the fiber structure in a sheet by treating the sheet with formaldehyde-free and acrylonitrile-free acrylic resin dispersions, whose resin components consist of acrylic or methacrylic esters, a small share of hydroxyalkyl esters of unsaturated carbonic acids, and, under certain circumstances, small quantities of acrylic or methacrylic acid. Even though textile sheets so treated have a higher wet tensile strength than those whose binders do not contain the hydroxyalkyl ester components mentioned, their wet tensile strength leaves something to be desired.
European Pat. No. A 19 169 describes aqueous dispersions which are used as binders for fiber non woven. The binders consist of a mixed polymerizate of acrylic or methacrylic esters or other monomers, and 3-10% by weight of units of acrylamide-glycolic acid. These binders are therefore examples of binders which do not yield any formaldehyde when heated. Since, however, textile sheets treated with these binders do not exhibit the desired degree of wet tensile strength, small quantities of N-methylolacrylamide are polymerized into the mixed polymerizates, which causes on increase of the wet tensile strength of the treated fiber sheets. However, the potential for the release of formaldehyde appears again.
European Pat. No. A96 230 describes coating materials which, as cross-linking binders, contain mixed polymerizates of acrylic monomers and a cross-linking system of acrylamido glycolic acid methylester-methylether and hydroxy, carboxy or amido-functional comonomers. During heating, the monomer units of the system undergo condensation reactions. The use of such mixed polymerizates as binders for textile sheets is not known. A need therefore continues to exist for a method by which bound textile sheets can be manufactured which exhibit improved wet tensile strength and which do not release formaldehyde when heated.